Thin-film-composite membranes comprising of self-assembled polyelectrolytes for separation of water from ethylene glycol by pervaporation

This work deals with a novel thin-film-composite membrane based on layer-by-layer self-assembly of polyelectrolytes onto an interfacially polymerized polyamide membrane for dehydration of ethylene glycol by pervaporation. Polyethyleneimine and poly(acrylic acid) were used as the polycations and polyanions, respectively. Compared to conventionally used microporous substrates for polyelectrolyte layer-by-layer buildup, the use of interfacially polymerized polyamide membrane as a substrate would significantly reduce the number of polyelectrolyte bilayers needed to form a permselective pervaporation membrane. For instance, the resulting membranes showed a good permselectivity flux with only two to three bilayers of the polyelectrolytes; a permeation flux of 0.4 kg/(m2 h) and a separation factor of 340 were obtained at 40 °C for a feed water concentration of 3 wt% using a membrane with three polyelectrolyte bilayers. For the separation of water from ethylene glycol using the polyelectrolyte/polyamide composite membranes, both the solution thermodynamics and the membrane permeability were favorable toward water enrichment in the permeate.